How many years passed between the building of the aqua appia and the completion of the pantheon

In response to the probable growing need for water, the censor Appius Claudius Caecus built the Aqua Appia in 312 BC. It was the procedure in Rome to entrust to the two 'censors' during their eighteen months of office the building of public works.

answer; (a) he was a u.s senator for 38 years;